Isomerization of hydrocarbons



Patented Mar. 21, 1950 ISOMERIZATION OF HYDROCARBONS Julian M. Mavity,Chicago, Ill., assignor to Universal Oil Products Company, Chicago,111., a

corporation of Delaware Application January 16, 1942, Serial No. 426,962

3 Claims.

The present invention relates to an improved process for the conversionof hydrocarbons of a saturated character. More particularly, it isconcerned with the production of branched chain paraflin hydrocarbons ofthe same or lower molecular weight from paraflin containing hydrocarbonoils, such as, for example, distillate fractions of petroleum.

More specifically, it is concerned with improvements in processeswherein isomerization of paraffin and naphthene hydrocarbons is efiectedby contact with metal halide catalysts of the Friedel- Crafts type, andparticularly aluminum chloride. This may be accompanied by the formationof branched chain paraflin hydrocarbons containing a fewer number ofcarbon atoms than the paraffins from which they are formed, such asisobutane, isopentane, isohexanes, etc.

The isomerization of saturated hydrocarbons is becoming increasinglyimportant commercially at the present time due to the fact thathydrocarbons of branched chain structure in the case of parafiinhydrocarbons are generally more reactive than their normal straightchain counterparts. For example, normal butane which is produced inconsiderable quantities in the production and primary distillation ofcrude petroleums is apparently not capable of being alkylated byolefinic hydrocarbons in the presence of catalysts, while isobutane canbe alkylated with olefins in the presence of a' number of dif ferenttypes of catalysts such as metal halides, sulphuric acid, hydrofluoricacid, phosphoric acid and others. By the alkylation of isobutane withbutenes, for example. octenes are produced which are readilyhydrogenated to isomeric octanes having high antiknock blending valuesin motor and aviation fuels. In the case of normally liquid parafiinhydrocarbons or mixtures containing such hydrocarbons in admixture withvarying amounts of naphthenes such as straight run gasoline fractions,isomerization produces compounds or hydrocarbon mixtures of improvedantiknock rating with minimum losses when conditions of operation areproperly regulated. The present improved process is applicable to theeflicient isomerization of normal butane, of normally liquidhydrocarbons or mixtures thereof either parafiinic or naphthenic or tothe treatment of essentially saturated gasoline fractions to improvetheir antiknock value. The process is applicable to the conversion of ahydrocarbon mixture of a saturated character containing parafflns. Thisconversion will involve, broadly speaking, the production of branchedchain paraflins of the same or lower molecular weight fromparaflin-containing oils in, for example, the

cracking of distillate fractions of petroleum such as naphtha fractionsto produce low-boiling parafiins such as isobutane, isopentane,isohexanes. etc., or in the isomerization of normal or mildly branchedchain paraiiins to more highly branched chain parafllns of the samenumber of carbon atoms. The process may be operated in such a mannerthat both types of reactions occur simultaneously.

In one specific embodiment the present invention comprises subjecting aprepared mixture of a saturated hydrocarbon, a hydrogen halide andhydrogen to contact with aluminum chloride hydrocarbon complexes in aprimary stage, fur-- ther contacting the hydrocarbon products from theprimary stage with granular aluminum chloride in a secondary stage whileseparating hydrocarbon-aluminum chloride complexes, returning saidcomplexes to the primary treating stage, fractionating hydrocarbonproducts from the secondary stage to separate hydrogen and hydrogenhalide which are recycled to the primary stage, and products comprisingbranched chain paraflins which are recovered as the product of theprocess, a fraction amenable to further isomerizing treatment which isrecycled to the primary stage and heavier hydrocarbonaluminum chloridecomplexes which are withdrawn from the process.

The features of the present improved process will be described in moredetail in connection with the attached drawing which showsdiagrammatically by the use of interconnected units in general sideelevation an arrangement of equipment in which the process may beconducted. The drawing is not restricted to any absolute or relativescale and the invention is not limited to the exact description given inconnection therewith.

Referring to the drawing, a hydrocarbon charge is admitted to the plantby way'of line I containing valve 2 to a charging pump 3 whichdischarges through line 4 containing valve 5 into a heating element 6disposed to receive heat from a furnace I. In the preferred operation ofthe process regulated amounts of hydrogen halide such as hydrogenchloride are introduced to line 8 containing valve 9 to pump orcompressor In which discharges through line H containing valve [2 intoline 4, and hydrogen is also preferably introduced by way of line I!containing valve I4 to a compressor I5 which discharges through line Itcontaining valve l1.

and also into line 4, so that a mixture of a hydrocarbon charge,hydrogen halide and hydrogen enters heating element 6.

During passage through heating element 6 the entering mixture is heatedto some temperature which is generally within the range of 50 to 125 0.,although depending upon the hydrocarbon charge and the degree ofisomerization or other conversion ultimately desired temperatures fromto 200 C. may be employed. Obviously, when subatmospheric temperaturesare used heater 8 may be by-passed or function as a cooler, althoughmeansfor efiecting the by-passing of the element 6 or utilizing thefurnace set-up as a cooler are not indicated in the drawing. The processis not limited in respect to the pressures which may be employed except.as they may influence the course of the desired reactions in connectionwith the temperature selected and other factors, and it is-within thescope of the present-invention to employ pressures as high as 20M) persquare in'ch, although as a rule pressx esortrcm about 100 to about 1000pounds persuaare inch are preferred. 4 A hydrogen halide such- 6.5hydrogen chloride is generally used in nemies: at least 0.01 mole permole of hydro- Hydrogen may or may not be employed depending upon-thetendency of the hydrocarbonstrr undergo undesirable decompositionreactions other than isomerizatiomand in general, it is seldom necessaryto employ more than 3 moles-of hydrogen permole of hydrocarbonundergoing'' 'treatment. The conditions utilized ifi-th'e'primarytreating stage wherein a hydrocarbon charge is contacted with thehydrocarbonm'etal halide 'complexes formed in the second stig'ewlll varyconsiderably depending upon the ekaet compdsitioncnd history of thecomplex. The heated -"materials from element 6 pass th'r'ou'gli' lihewcontaining valve 19 to enter the bottom of a'p'rimary reactor 20 whichpreferably has a section?! filled with granular and relatively 'iner'tpacking material which functions to distribute the down-flowing streamsof liquid hydrocarbon-metal halide complex introduced from me Ill andarising at a point and in a manner to later described. Reactoril! isprovided with'an'upper manhead 22 for the introduction offfillingmaterial and a lower manhead 23 for its' conve'nient removal ifnecessary. This reactor is also furnished with a lower draw line 2containlng' valve iii-which "permits the reiection of thehydrocarbon-metal halide complex after its use 'in'the primary stagesince there is generally no benefitdn reusing this material.

It has been determined and constitutes a feature of'the presentinvention that hydrocarbonallumlnum chloride complexes formed whensaturated hydrocarbons are contacted with granular aluminum chloridecatalysts, still have isomerizing potency. These complexes areapparently formed by the union of unsaturated radicals with the aluminumchloride catalyst, the unsaturated components having been formed byincidental and usually minor decomposition reactions. Use is thereforemade of these complexes for a prelllliinary=tr'eathint-'of hydrocarbonsto be isomeized and this preliminary treatment produces several benefitsunder which may be mentioned the utilization of'the partly spent primarymetal halide catalysts, the preliminary purification of hydrocarboncharges which may at times contain-incidental constituents comprisingolefins, aromatics and-compounds containing omen-or siflfurmndapartial'isomerization-of the hydro- 5 carbon charge, this isomerization beingsubstan-' tially completed in the second stage wherein it is contactedwith a fresh metal halide catalyst. The products from primary reactor 20pass through line 25 containing valve 21 and into a secondary reactorcontaining a bed of granular aluminum chloride.

For insuring continuous operations secondary reactors are utilized inmultiple arrangement and may be connected so as to be used in parallel,series of parallel-series connection. Thus, line 25 leads to line 28containing valve 29 leading to reactor 38, and also to line 54containing valve 45 leading to a similar reactor 46. Each of thereactors is similarly equipped with lines so that the materials from theprimary stage may enter the bottom of the reactor below a fixed bed ofgranular catalyst, the lower layer hydrocarbon aluminum chloride complexmay be withdrawn, and the reaction products may be withdrawn from thetop and passed to subsequent fractionatie-n. Thus, secondary reactor 33contains a bed of granular catalyst 34 while reactor 46 contains ananalogous bed of granular material 41. Reactor 35 has a manhead 32 forthe admission of granular aluminum chloride which corresponds to manhead48 on .reactor 46, and a lower manhead for the removal of contaminatedmaterial, which corresponds to manhead 49 on reactor 50. Reactor 30 hasa lower draw line -33 containing valve 34 through which the said 1W6!"layer material may he released, and a branch line 35 containing valve'36 leading to line-31 from which point the lower layer material may besent back to the primary treating stage. Reactor #6 has similar drawline so containing valve 51 {or the rej coir-ion of lower layer materialand a branch line 52 containing valve 53 and leading to-lrne 31. Thelower layer complex withdrawn from either secondary stage reactor, asrepresentingany multiple arrangement, passes through line 3? containingvalve 38 to a pump 39 which discharges through line #0 containing valve41 and into the top of reactor it above the filling materill as alreadyindicated.

For permitting series operation in which primarily treated materials arepassed first, through the metal halide bed in reactor 30 and thenthrough a corresponding bed in reactor 46, the upper exit line 56containing valve 5"! has a branch line 52 containing valve 43 andleading to line (it, so that with valve '45 closed the reactants enterthe bottom of'reactor 45 below the bed of catalyst. Similarly, upperseries line 58 containing valve 59 has a branch line 5t containing valve55 which leads to line 23 so that with valve 29 closed the effluentmaterials from reactor 46 may pass through reactor 31!.

During passage of the partially isomerized charge from the primarytreating stage through: the granular metal halide catalyst in the secondstage, isomerization is substantially completed and in the course of thereaction the so-called lower layer is formed consisting of hydrocar-:ban-metal halide complexes. As these are :formed they fail downwardlycounter-current to the .-'ascending reactants so that there is acontinuous consumption of metal halide. As the depth of the catalyst beddecrea es, more may be addedby intermittently cutting the reactors outof the circuit and introducing -more catalyst through the uppermanheads, the stream of reactants passing through other parallelreactors so mmthe continuity of operation is not interruptell;-

After the second stage isome'r iz'ing tre'atment,-'--

the products from the reactors are passed to fractionation, through line56 containing valve 51, if reactor. 30 is at the end of the second stageof treatment or from line 58 containing valve 59 if reactor 46 is lastin order. The exit lines from the secondary stage all enter a header 60containing valve 6| which leads to a fractionator 62 as indicated in thedrawing, although this fractionator merely diagrammatically represents afractionating zone in which may be included any number of suitablydesigned and interconnected fractionators for effecting eflicientseparation of materials to be recovered, recycled and rejected from theprocess. As indicated in the drawing,

light gases including hydrogen chloride and hy-' drogen are taken offthrough line 63 containing valve 64 and leading to recycle pump 65 whichdischarges through line 66 containing valve 61 and back to process inletline 4. The isomer fraction such as isobutane in case normal butane istreated, may be withdrawn at a next lower level through line 66containing valve 69 passed through condenser 10 and thence through lineH containing valve 12 to a final receiving drum 13 provided with aconventional gas release line 14 containing valve 15 and a liquid drawline 16 for isomer product provided with valve 11. Fractions amenable tofurther isomerization treatment are withdrawn at the next lower levelthrough line 78 containing valve I9. to recycling pump 80 whichdischarges through line 8| containing valve 82 back to process inletline 4'. In isomerization of normal butane the material recycled .atthis point is the unconverted charge. Higher boiling fractions producedincidentally to the main isomerization reactions and of a character notadapted to further isomerization without undue losses and contaminationof the catalyst may be withdrawn through line 83 containing valve 84.

I The foregoing description utilizes in general the procedure whichcharacterizes the present process although other modifications thanthose described may be added which facilitate operations withoutessentially altering the process. For example, a means may be providedfor operating the primary reactor 20 at different temperature andpressure conditions than secondary reactors and 46 either by theintroduction of heating and cooling devices alongthe line of flow of thereactants or the recycled materials by the introduction of additionalpressuring pumps. Similarly, means may be provided for maintainingsubstantially constant temperature conditions throughout the reactorssuch as submerged pipe coils which convey heating or cooling fluids.

The relative amounts of hydrogen and hydrogenhalide in relation tohydrocarbon charge may also be varied as a means for controlling thenature of the reactions.

The present process is most completely adapted to the utilization ofgranular and substantially anhydrous aluminum chloride in'secondaryreactors and the utilization of hydrogen chloride as the hydrogen halidefor promoting the isomerization reactions in contact with the aluminumchloride. Obviously, when hydrocarbon charging stocks of diversecharacter are treated it will be necessary to determine by trial thebest cono ditions of operation. In the case of gasoline fractions whichare to be isomerized for the improvement of their antiknock value,conditions treating plant similar to the one described in connectionwith the drawing, at a temperature of 100 C. under a pressure of 500lbs., per square inch at a liquid charging rate equivalent to 0.25volume of liquid fraction per hour per volume'of secondary reactionspace, that is the space occupied by granular aluminum chloride.

Operations were continued over a period of approximately 200 hoursduring which time there was an average yield of 95% of octane numberproduct.

I claim as my invention:

1. A process which comprises contacting relatively low-boilinghydrocarbon material with a bed of solid anhydrous sludge forming metalhalide catalyst of the Friedel-Crafts type under hydrocarbon conversionconditions, withdrawing from said bed an active metal halide sludgeproduced therein concomitantly with said conversion, and contactinghydrocarbons from said contacting step with said sludge under conversionconditions to continue said conversion through utilization of catalyticactivity of said sludge.

2. The process of claim 1 in which said metal halide is aluminumchloride.

3. The process of claim 1 in which said hydro REFERENCES CITED Thefollowing references are 'of record in the file of this patent:

UNITED STATES PATENTS I Number Name Date 2,222,012 Amos Nov. 19, 1940 I2,223,180 Lynch et al. Nov. 26, 1940 2,265,548 Schuit Dec. 9, 19412,265,870 Schuit Dec. 9, 1941 2,266,012 DOuville et al Dec. 16, 19412,271,043 Van Peski Jan. 27, 1942 2,280,710 Lynch Apr. 21, 19422,280,748 Calhoun Apr. 21, 1942 2,281,924 deSimo et al May5, 19422,301,615 Chenicek Nov. 10, 1942 2,306,261 Crawford Dec. 22, 19422,307,053 Lynch Jan. 5, 1943 2,308,561 Marschner Jan. 19, 1943 2,314,297Watson Mar. 16, 1943 2,317,241 Ackerman et al. Apr. 20, 1943 2,330,206Dryer et a1. Sept. 28, 1943 2,330,754 Skelton et al. Sept. 28, 19432,331,429 Sensel et al. Oct. 12, 1943 2,347,266 Ipatiefl. et al. Apr.25, 1944 2,356,190 Voorhies Aug. 22, 19 4

1. A PROCESS WHICH COMPRISES CONTACTING RELATIVELY LOW-BOILINGHYDROCARBON MATERIAL WITH A BED OF SOLID ANHYDROUS SLUDGE-FORMING METALHAL IDE CATALYST OF THE FRIEDELCRAFTS TYPE UNDER HYDROCARBON CONVERSIONCONDITIONS, WITHDRAWING FROM SAID BED AN ACTIVE METAL HALIDE SLUDGEPRODUCED THEREIN CONCOMITANTLY WITH SAID CONVERSION, AND CONTACTINGHYDROCARBONS FROM SAID CONTACTING STEP WITH SAID SLUDGE UNDER CONVERSIONCONDITIONS TO CONTINUE SAID CONVERSION THROUGH UTILICATION OF CATALYTICACTIVITY OF SAID SLUDGE.